The UAE authority has converted many of its heritage buildings into museums due to the cultural value of these buildings and their potential to promote tourism economy. Nevertheless, these buildings were not designed to host valuable artefacts and thus ensuring their operation as museums is a crucial question that is investigated in this research. The objective is to evaluate the daylighting levels in the display room using different Window-To-Wall ratios (WWRs) and the potential risks on the historical artefacts. At the outset, the study conducted several site visits to collect information and take measurements in the real lighting environment of these buildings. This helped to survey the displayed artefacts and classify them into categories based on their sensitivity to light and define the lighting characteristics of the display room. Statistical analysis was performed on building data gathered from images and architectural drawings to identify the measures of the different spatial and building elements. To investigate the daylight performance as a function of WWR change, 3D models with three ranges of WWRs (5%, 9%, and 15%) were developed applied to a medium size exhibited space with courtyard windows on the southwest orientation. Simulations were performed for each category of the artefacts considering a large number of sensors distributed horizontally in the room to cover all possible locations of artefacts. The tested metrics were Daylighting Autonomy (DA) and the Useful Daylighting Illuminance (UDI). The results revealed high levels of illuminance in the exhibited spaces for all tested ranges of WWRs, especially for the high sensitive artefacts; and confirmed that the change of WWR from 5-15% could lead to extreme risks. The study recommends minimise WWR and provide shading in order to enhance the overall lighting environment and reduce light exposure on the artefacts.